20. Hosts A and B are each connected to a switch S via 100-Mbps links as in Figure 1.21. The propagation delay on each link is20 s. S is a store-and-forward device; it begins retransmitting a received packet 35 s after it has finished receiving it. Calculate the total time required to transmit 10,000 bits from A to B (a) As a single packet. (b) As two 5000-bit packets sent one right after the other.